/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.runners.core.triggers;



import com.bff.gaia.unified.sdk.annotations.Experimental;

import com.bff.gaia.unified.sdk.state.TimeDomain;



/**

 * A trigger that is equivalent to {@code Repeatedly.forever(AfterWatermark.pastEndOfWindow())}. See

 * {@link RepeatedlyStateMachine#forever} and {@link AfterWatermarkStateMachine#pastEndOfWindow} for

 * more details.

 */

@Experimental(Experimental.Kind.TRIGGER)

public class DefaultTriggerStateMachine extends TriggerStateMachine {



  private DefaultTriggerStateMachine() {

    super(null);

  }



  /** Returns the default trigger. */

  public static DefaultTriggerStateMachine of() {

    return new DefaultTriggerStateMachine();

  }



  @Override

  public void onElement(OnElementContext c) throws Exception {

    // If the end of the window has already been reached, then we are already ready to fire

    // and do not need to set a wake-up timer.

    if (!endOfWindowReached(c)) {

      c.setTimer(c.window().maxTimestamp(), TimeDomain.EVENT_TIME);

    }

  }



  @Override

  public void onMerge(OnMergeContext c) throws Exception {

    // If the end of the window has already been reached, then we are already ready to fire

    // and do not need to set a wake-up timer.

    if (!endOfWindowReached(c)) {

      c.setTimer(c.window().maxTimestamp(), TimeDomain.EVENT_TIME);

    }

  }



  @Override

  public void clear(TriggerContext c) throws Exception {}



  @Override

  public boolean isCompatible(TriggerStateMachine other) {

    // Semantically, all default triggers are identical

    return other instanceof DefaultTriggerStateMachine;

  }



  @Override

  public boolean shouldFire(TriggerStateMachine.TriggerContext context) throws Exception {

    return endOfWindowReached(context);

  }



  private boolean endOfWindowReached(TriggerStateMachine.TriggerContext context) {

    return context.currentEventTime() != null

        && context.currentEventTime().isAfter(context.window().maxTimestamp());

  }



  @Override

  public void onFire(TriggerStateMachine.TriggerContext context) throws Exception {}

}